Need help with rotor phasing

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Other than sometimes kicking back, I noticed when I had the cap off I looked at where the rotor had been firing on the towers. It is only firing on about three quarters of the towers on each cylinder. You can tell by the marks left on the towers. I cut a large hole in the side of the cap so I could actually see the rotor when it is firing with my timing light. It looks like it is firing just like the marks that was left. My initial shows 22 btdc. It is like the rotor needs to be turned about 7 degrees to fire on all the tower surface
 
downsr said:
Other than sometimes kicking back, I noticed when I had the cap off I looked at where the rotor had been firing on the towers. It is only firing on about three quarters of the towers on each cylinder. You can tell by the marks left on the towers. I cut a large hole in the side of the cap so I could actually see the rotor when it is firing with my timing light. It looks like it is firing just like the marks that was left. My initial shows 22 btdc. It is like the rotor needs to be turned about 7 degrees to fire on all the tower surface
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Oh gee whiz forget about that pattern, the rotor is constantly moving about under there from about 1000 to 3000 or even a little higher depending on when it starts it's march and at what rpm it finishes. That is normal. If it hits the right tower that is all that is important.
 
If kicking back against the starter is the issue I would back the initial timing to 15° and try from there. With your combination there is no reason it won't idle with 10 or 15° of initial timing and you tune from there. Initial timing is not for performance it is for starting and idling. The mechanical advance curve is for performance. Are you checking your initial with the distributor vacuum line disconnected and plugged? What rpm are you checking it at? Is the distributor curve set to advance at a low rpm?
 
The vac is disconnected and the mechanical doesn't start till 1200 rpm checking initial around 900 rpm with light
 
downsr said:
The vac is disconnected and the mechanical doesn't start till 1200 rpm checking initial around 900 rpm with light
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Knowing that I would say too much initial. One of the other guys mentioned a switch. I have a buddy that used to run a Small block Corvette in Division 5 NHRA. He had the ignition power wired through a toggle switch. They would spin the starter then light the fire with the switch. I don't know how much initial they were running but it was too much for the starter. Worse when the engine was hot.
 
I will call bullet camshaft and see if they have any suggestions on initial timing. A cam with 235 to245 duration calls for around 18 to 22 degrees initial with the information I have gathered from different sources. It will not kick back if I turn the engine over without firing it with a remote starter first. I am just trying to make sure the phasing is correct. I never had this problem until last fall when I changed the distributor. I have changed starter , relay on fire wall and carburetor from a 750 to a 650 . Since it does not kick back if I rotate the engine first without firing it seems to be ignition related.I know they have had some problems with phasing on some of there distributors.I am going to try what AJ/FORMS suggested tomorrow and give msd a call Tuesday
 
AJ/FormS said:
You have a book that lists a spec for a 416/.570lift solid roller? lol
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I guess you don't read the whole thing but what I said was I set my motors at 10* to start ad go from there.
I do things a little different than other people. If the rotor is past the tower I can adjust the vacuum advance pull rod to move the pick up coil and that puts the rotor to tower in a different place. I like JB Weld but its defiantly not the best plastic glue and I wouldn't use it on a rotor or cap to re position it. The book I was talking about was a 1970 mopar factory service manual and it was a reference for a 340 and was for a starting point sense it wont start at 44* or 30* or even 18* LOL.
Sorry for any confusion I caused you AJ
 
I just have a hard time believing you can't set up a dist to crank at 10* advance to 18 -20* at idle and then adjust it to give you what you want at full advance.
I do it with a simple degree wheel before it goes in the motor and then change the springs to fine tune if need be.
 
I had this exact thing happen when I welded up the advance slots and breaker plate on a stock distributor once.
I was rushing through the job, and welded the plate in a too far advanced position.
As a result, it tried to kick back every time I tried to start it, regardless of where I positioned the distributor.
It was trying to fire between the posts...drove me crazy!!
 
Downsr
I wonder if you are confusing the Timing of the spark event with where it's going. These are two separate things
When the spark occurs, is controlled by the ECU in response to, when the magnetic pick-up senses the reluctor passing by. The ECU doesn't care where the rotor is at this time. When it senses the magnetic disturbance at the pick-up, POW! it fires off a signal to the coil, and then waits. When it senses another disturbance, then POW! it fires off another signal to the coil.
Every time the coil receives a signal, POW! it generates a huge voltage spike, which travels up the wire into the cap and across the rotor, where it waits for the rotor to come near enough to a tower that it can hop across to. Then POW! it jumps across and continues to it's destination.
See that? It sits and waits on the rotor tip. It doesn't wait for a particular place on the tower to jump to. It ain't fussy. It will just nail the closest good metal it sees.It just better be the right tower it is coming up to.
If you set your timing say way to far advanced, then perhaps the wrong tower will be nearer to the rotor than the correct one. The spike don't care it will just jump.

Now here's the thing about the starter kick back. As the starter is cranking the engine, each time a piston comes to the top you can measure how much pressure is being generated in the chamber.With a compression tester you might see a peak pressure of 160 psi after several revolutions. But on the first compression event, you might see only 100 psi
That pressure will peak at TDC if unlit. But at 22* BTDC that pressure may already be at 80 or 90 psi. On a 4 inch piston this might be 1100 or 1200 pounds of force. That piston is not interested in continuing. It wants to go back. But the starter is driving it. It has no choice. Then the spark event takes place. And the A/F charge begins to burn, making hot gasses that increase the pressure even more. The peak pressure is not supposed to occur until the piston is well past TDC where the pressure can be transferred to the crank by the rod, and it becomes power to move the car. If you start the fire too early, the pressure builds too high for the starter to continue driving it. Then the pressure tries to push the piston back down the way it came.
To overcome this you have three choices; 1) get a more powerful starter, 2) reduce the cylinder pressure, 3) get a heavier flywheel.
Reducing the cylinder pressure can be done several ways, but the easiest is to start the fire later, by reducing the initial timing.
 
Here is an experiment;
Turn your crank to 22* BTDC compression #1cylinder.(Your chosen, perhaps arbitrarily, initial timing)
Pull the cap off and get it out of the way.
Take the coil wire out of the cap and near-ground it.
Loosen the the Distributor. Just so you can turn it a wee bit.
Eyeball the relationship of the magnetic pick-up to the reluctor. They should be sorta directly across from each other.
Turn the key to RUN.
Push the v-can several degrees towards the firewall. Then slowly pull it back towards the rad while simultaneously watching and listening for the spark event to occur at the near-grounded coil wire. SNAP! there it is! Stop pulling and eyeball the relationship again. It should appear much the same as when you first saw it. Repeat this several times. If the snap does not occur, rotate the distributor slightly faster, some pick-ups are lazy.
Notice the coil wire did not care where the rotor was.
Turn the key off
Go back to the crank and rotate it to set the timing marks to 16*BTDC.
Go back to the Dist and push the V-can back several degrees.
Turn the key to RUN again
Return to the Vcan and give it a light smooth tug until the snap occurs, Repeat several times, and lock the D down.
Again the rotor was out of the equation.

Now grab a sharpie and mark the position of the rotor tip on the outside of the D next to where the cap will sit
Grab the rotor and give it a little twist to see which way the rotor turns and how far.This distance has to be compensated for in the positioning of the #1 tower. Make a corresponding mark next to the first mark where the rotor tip will eventually be as the rpm goes up.
The number 1 tower will have to be the nearest tower to those marks while the engine is running. Grab the cap and make a mark on it,at the #1 tower location,
where the cap sits on the D body.
Now set the cap back on the D,properly indexed, and observe the two sharpie marks you made on the D. Ideally they will be straddling the #1 tower mark. But they don't have to be. As long as the rotor is always closer to the #1 tower than to any other then it will spark correctly.
But if this experiment shows that at some rpm, the rotor will be closer to an adjacent tower, than to the #1 tower, THAT HAS TO BE FIXED.


Now put it all back together and fire it up. Set the idle timing to 16*.
Rev it up as high as it takes to make the advance marks stop moving, or 4000rpm max. Record the number, and the rpm. If it is less than 36* go for a ride.If more than 36* don't floor it. If it is more than 37* or less than 34* then we are gonna have to modify the dizzy, OOps D!
But first, see how it likes 16*. Take it for a ride and warm it up good. Come home. Shut it off,and immediately attempt a restart. If it fires right up without kickback, Shut it off and wait 10 minutes and try it again. If it is still alright,make a note somewhere in your notebook that 16* was alright.
Then the tune begins.
 
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AJ/FormS said:
Here is an experiment;
Turn your crank to 22* BTDC compression #1cylinder.(Your chosen, perhaps arbitrarily, initial timing)
Pull the cap off and get it out of the way.
Take the coil wire out of the cap and near-ground it.
Loosen the the Distributor. Just so you can turn it a wee bit.
Eyeball the relationship of the magnetic pick-up to the reluctor. They should be sorta directly across from each other.
Turn the key to RUN.
Push the v-can several degrees towards the firewall. Then slowly pull it back towards the rad while simultaneously watching and listening for the spark event to occur at the near-grounded coil wire. SNAP! there it is! Stop pulling and eyeball the relationship again. It should appear much the same as when you first saw it. Repeat this several times. If the snap does not occur, rotate the distributor slightly faster, some pick-ups are lazy.
Notice the coil wire did not care where the rotor was.
Turn the key off
Go back to the crank and rotate it to set the timing marks to 16*BTDC.
Go back to the Dist and push the V-can back several degrees.
Turn the key to RUN again
Return to the Vcan and give it a light smooth tug until the snap occurs, Repeat several times. and lock the D down.
Again the rotor was out of the equation.

Now grab a sharpie and mark the position of the rotor tip on the outside of the D next to where the cap will sit
Grab the rotor and give it a little twist to see which way the rotor turns and how far.This distance has to be compensated for in the positioning of the #1 tower. Make a corresponding mark next to the first mark where the rotor tip will eventually be as the rpm goes up.
The number 1 tower will have to be the nearest tower to those marks while the engine is running. Grab the cap and make a mark where the cap sets on the D body, at the #1 tower location.
Now set the cap back on the D, and observe the two sharpie marks you made on the D. Ideally they will be straddling the #1 tower mark. But they don't have to be. As long as the rotor is always closer to the #1 tower than to any other then it will spark correctly.
But if this experiment shows that at some rpm, the rotor will be closer to an adjacent tower, than to the #1 tower, THAT HAS TO BE FIXED.


Now put it all back together and fire it up. Set the idle timing to 16*.
Rev it up as high as it takes to make the advance marks stop moving. Record the number, and the rpm. If it is less than 36* go for a ride.If more than 36* don't floor it. If it is more than 37* or less than 34* then we are gonna have to modify the dizzy, OOps D!
But first, see how it likes 16*. Take it for a ride and warm it up good. Come home. Shut it off,and immediately attempt a restart. If it fires right up without kickback, Shut it off and wait 10 minutes and try it again. If it is still alright,make a note somewhere in your notebook that 16* was alright.
Then the tune begins.
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Well said AJ!
 
AJ doesn't understand electricity if he thinks it sits and waits for a place to go!
 
only vac adv will change the rotor phasing position, not RPM so while idling if you plug the can into manifold vacuum you can check RP with a 1/2" hole in the top flat of the cap 2/3 of the way between the center dist cap terminal and the #1 dist cap terminal & the rotor will swing to the most CCW clocking position (on a SB).
 
brian6pac said:
Rapid Robert has it right. congrats
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Thank you brother. EDIT on the JB weld I do not glue the plastic per se but after I widen the notch in the upper dist metal shaft I use it on the opposite side to restore the notch width to its original dimention so the rotor "land" will fit snugly down into it. its alot of filing so I started drilling a new roll pin hole in the reluctor. I drill the hole aways in from the ID then file it outward till it breaks free to the ID with a mini rat tail file. careful measureing required but there is alot of room to repeat.
 
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Makes my head hurt. I guess I take way too much for granted that the rotor tip and the base are where they should be as well as the reluctor compared to the shaft. You guys that are good with this continue while I just stand back and learn a bit. Hell, I just learned the hard way that Edelbrock carbs don't like 10+ pounds of fuel pressure. I have been in the car hobby since the last century and I am still learning! tmm
 
brian6pac said:
simple things they take way to far. misunderstood
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the internet does have a few downsides but the perks are very well worth it. You tube is the best goldmine I have discovered so far. I had a coolant leak that was eluding me (wouldn't hold psi even before fireup so no coolant to spot) & guy on there on a video said to put a rag in a 1 gallon paint can with some baby oil & set it on fire! & plumb that into the cooling system & with its own built up psi you will spot the leak & wah la I found it right away & a shop want $45 hr to hookup their smoke machine to it & the car was not race ready & would have to have been towed or the eng pulled. EDIT the best thing I like about FABO is when someone posts a problem multiple people (as in dozens) will contribute toward the solution! just takes time (not a problem when you are retired).
 
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Rapid Robert said:
only vac adv will change the rotor phasing position, not RPM so while idling if you plug the can into manifold vacuum you can check RP with a 1/2" hole in the top flat of the cap 2/3 of the way between the center dist cap terminal and the #1 dist cap terminal & the rotor will swing to the most CCW clocking position (on a SB).
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Let me get this straight vac advance can will affect (change) rotor phasing But. mechanical advance (rpm) will not???????
 
Cudafever said:
Let me get this straight vac advance can will affect (change) rotor phasing But. mechanical advance (rpm) will not???????
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Took me a sec without coffee, but yeah. The reluctor and rotor are on the distributor shaft with the mechanical advance. The magnetic pick up is on the breaker plate that the vac advance pulls on.
 
Always a good day when you can answer your own questions! (I wished I could do that!). You have some leeway on positioning cuz they are both wide & for every degree of vac adv it will shift the rotor 0.0234" so if the rotor "arc" circumferential distance stays "close" to the cap terminal then you are good. also there is the radial distance from the tip to the cap & ideal is .015" & NAPA has an Echlin rotor MO3000 with a .060" longer blade for $8.xx out the door or you can drill out the rivet & add a longer tang. best is a black or brown cap with BRASS terminals & you can dremel em to keep the brass terminal edges clean/sharp as it takes less voltage to jump from sharp edges than it does from rounded edges. absolutely reduce the lower shaft axial clearance to .005" with the speedway motors $5 shim kit. EDIT when you shine your light in the hole you will see that only the can alters positioning
 
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Cudafever said:
Let me get this straight vac advance can will affect (change) rotor phasing But. mechanical advance (rpm) will not???????
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Yup True dat. If you look at some other dist designs, especially V6/ 4 whanger, some had weird wide rotor contacts so that the phasing would remain in alignment

rotor-riveted.jpg


distributor_rotor_body_marked_no1plug_contact_point.jpg
 
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